Apparatus for selective drying



April 7, 1954 c. L. CALOSI ET AL 2,676,416

APPARATUS FOR SELECTIVE DRYING Filed March 16, 1951 hum rues Cmwo L. cnLasx HER/MAIN Gan/7W5? RUMWBA'PG Patented Apr. 27, 1954 UNITED STATES PATEN T OFFICE APPARATUS FOR SELECTIVE DRYING Carlo 'L.

Gunther Mass., a corporation I Application March 16, 1951, Serial No.

2 Claims.

This invention relates to methods and apparatus'for the selective drying of wet deposits. on a web of material.

It is frequently desirable, for example, in printing, to dry Wet deposits on brittle.

It has been found that may be used to dry var ous types of material to dry the deposits without excessive drying of the web.

The foregoing and other advantages, objects and features of the invention will be better of one embodi- The a-node-cathodeg-circuit is supplied with a potential from a source I! that is pulsed at It Newton, turing Company, Newton,

Calosi," Cambridge, and Herman Rudenberg, to R-aytheon Manufac assignors of.-. Delaware ...by1a source, of keying pulses 20. The magnetron and as I4 is coupled to the waveguide 3 through a loop 2| and a coaxial cable 22 with a central confor the heat generated to difluse into the full thickness w of the Web l0 having a thermal difiusivity d. The time For example, with a pulse duration of ten times the thermal diffusion time of the sheet, the whole sheet is heated almost a pulse duration equal to the diffusion time, only two-thirds of that power is needed to achieve the same surface temperature. At

only one-quarter of the original power is needed and at only one-eleventh of the original power is required to obtain the same surface average power need be applied to obtain the characteristics of the materials used permit of: U

a longer exposure by dimensioning the wave guide in the plane along which the web passes so that at the speed of travel of the. web any particular portion of the web will only be in the: electromagnetic field for the desired length oi time.

For example, if the web travels across the width.

to of the wave guide i3 at a speed 12, it will be ex. posed to the held for a time This. accomplishes the same purpose as pulsing the source of radio frequency energy by limiting the total energy a given area is permitted to absorb. However, it is obvious that pulses may be made of shorter duration, in the order of microseconds, as compared to the transit time of the web in the wave guide, at best in the order of milliseconds. Thus for most purposes the use of a pulsed source of radio. frequency energy as shown in Fig.1 will result in greater flexibility.

Fig. 3 shows an embodiment of they invention dependent upon transit time for determining the amount of radio frequency energy to which an individual area of? the web and deposits is exposed. As before, the web fl! enters the slot I2 in the. wave. guide or cavity 13 where it is exposed to an electromagnetic field introduced into the cavity l3 by a coaxial cable 22, the center conductor 23 of which protrudes into the cavity l3 to introduce the radio frequency energy and create the electromagnetic field. A similar wave guide and coupling means could be used for the embodiment shown in Fig. 1. Certain details of the radio frequency and electrical circuits have been omitted in the interest of clarity as these details form no: part of the present invention and may take any one of several wellknown forms;

This invention is not limited to the particular details of construction, materials and proce'sses described, as many equivalents will suggest themselves to those skilled in the art. It is accordingly desired that the appended claims be given a broad interpretation commensurate with the scope of the: invention. within the art.

What is claimed is:

1. Apparatus for drying a wet deposit on a web of material, comprising a metallic enclosure defining a cavity, means for inserting the web to be dried into the said cavity and means for applying to the cavity pulses of radio frequency energy of an duration in the order of microsecends snmcient. with reference to the thermal difiusiv-ity of the web to dry the deposits while leaving. a. substantial portion of the original moisture in the web.

2; Apparatus for heating a wet deposit on a web of material comprising a conductive enclosure defining, a cavity, means for inserting the web to be heated into said cavity, and means for applying to the cavity pulses of radio frequency energy of a duration in the order of microseconds sufficientwith reference to. the. thermal diffusivity of. the webto raise; the temperature of the deposit to the vaporizing point of their solvents while leaving the web. at a temperature substantially below the vaporizing points oil. its solvents.

References Citedv the file of this patent UNITED PATENTS 

